A runny nose is a symptom of many conditions. It’s characterized by mucus draining or dripping from the nostril.

Mucus is a protective substance produced by the mucous membrane, a type of tissue lining the nasal cavity. Mucus moistens the air you breathe, and it acts as a barrier to keep dust, pollen, and bacteria out of your lungs.

Your nose produces mucus every day, yet you probably don’t notice because it mixes with saliva and drips down the back of your throat.

Sometimes, irritation or inflammation in the nasal passage can lead to increased mucus production. When this happens, excess mucus can drain or drip from the nose.

Here’s a look at 15 common causes of a runny nose.

Indoor and outdoor allergies can trigger an allergic response. Allergens include:

  • dust
  • pollen
  • ragweed
  • pet dander

Allergens cause symptoms such as sneezing, a headache, or a sore throat. These inhaled particles can also irritate the nasal passage, resulting in excess mucus and a runny nose.

To cope with allergies and reduce drainage from the nose, limit exposure to substances that trigger a reaction. Many over-the-counter (OTC) antihistamines can block histamine and stop an allergic response.

If these medications don’t work, ask your doctor about prescription antihistamines.

The common cold, or an upper respiratory infection, causes inflammation in the mucous membrane lining of the nose, resulting in too much mucus. In addition to a runny nose, the common cold can sometimes cause nasal congestion.

Other symptoms include coughing, a sore throat, and fatigue. There isn’t a cure for the common cold, but OTC cold medications can help relieve symptoms. Getting plenty of rest, taking vitamin C, and drinking hot liquids may help you feel better sooner.

Many people have the misconception that antibiotics are necessary to treat common cold symptoms. This isn’t the case. Antibiotics should only be used to treat bacterial infections, such as a sinus infection. They aren’t effective at treating viral infections.

Sinusitis (sinus infection) is a complication of the common cold. It occurs when the cavities around your nasal passage become inflamed. This inflammation also triggers an increase in mucus production in the nose.

Other symptoms of sinusitis include a headache, nasal congestion, and facial pain.

Treatment can involve pain medication, use of a nasal corticosteroid to stop inflammation, or an antibiotic to kill the bacterial infection.

With this condition, the wall between your nasal passage becomes displaced or crooked on one side. Some people are born with a deviated septum, but it can also result from an injury to the nose.

A deviated septum can lead to repeated sinus infections and inflammation around the nasal passage, causing a runny nose.

Your doctor may recommend an antihistamine or a nasal steroid spray to manage this symptom. If this doesn’t work, surgery can correct a deviated septum.

The flu virus also causes inflammation in the mucous membrane of the nose. The flu is highly contagious and other symptoms can include:

  • fever
  • muscle aches
  • chills
  • headache
  • congestion
  • tiredness

OTC cold or flu medications can help relieve symptoms and reduce pain. Ingredients in these medications typically include a decongestant, a fever reducer, and a pain reliever.

Flu symptoms may improve within one to two weeks.

Even though medication is available to help relieve excess mucus production, a few may trigger a runny nose in some people.

Possible culprits include:

Read the label on medications for a list of common side effects. When a medication triggers a runny nose, this is due to nonallergic rhinitis.

Nonallergic rhinitis (vasomotor rhinitis) is also characterized by inflammation in the nasal passage and mimics hay fever (runny nose and sneezing). Yet, these symptoms are due to an unknown cause and aren’t triggered by histamine or an allergen.

In addition to medication-induced nonallergic rhinitis, other factors that can trigger this form of rhinitis include a change in temperature, bright sunlight, or an underlying health problem.

Oral antihistamines are ineffective for nonallergic rhinitis, but you may find relief with a nasal antihistamine or a saline nasal spray.

A hormonal imbalance can also cause inflammation and enlargement of the nasal blood vessels, resulting in nonallergic rhinitis. This can happen during puberty and if you take birth control pills or hormone replacement therapy.

A nasal antihistamine or saline nasal spray may relieve symptoms.

Dry air doesn’t only dry out the skin, it can also dry out your nasal passage. This disrupts the fluid balance inside of your nose, causing an inflammatory response and triggering a runny nose.

This can happen in cold weather or when there’s dry air inside of your home due to heat. To help manage dry air inside the home, use a humidifier to add moisture back into the air. You should also wear a scarf to cover your mouth and nose when going outdoors in the winter.

These benign growths on the lining inside the nose are due to an inflamed mucous membrane. When the mucous membrane becomes inflamed, excess mucus production brings on a runny nose and postnasal drip.

Other symptoms of a nasal polyp include:

  • loss of smell
  • sinus pressure
  • snoring
  • headache

Your doctor can prescribe a nasal corticosteroid spray to shrink a polyp. They may also prescribe an antibiotic to treat an accompanying sinus infection.

Depending on the severity of a polyp, sinus surgery can remove the growth.

Even though nasal sprays can reduce inflammation in the nose, overuse can have a rebound effect and make nasal symptoms worse.

Typically, you shouldn’t use an OTC nasal spray for more than five days in a row. Using a nasal spray in the long term can lead to chronic sinus infections, which can trigger a runny nose. Once you stop using a nasal spray, nasal symptoms may improve within a few days or weeks.

This is a virus that causes cold-like symptoms and infections in the lungs and respiratory tract. It can occur in children and adults. An infection in the respiratory tract can lead to inflammation in the nasal passage and a runny nose.

Other common symptoms include:

  • congestion
  • dry cough
  • low-grade fever
  • sore throat
  • headache

Treatment involves:

  • plenty of fluids
  • a fever reducer
  • saline nasal drops
  • an antibiotic, if there’s a bacterial infection

Severe infections may require hospitalization.

Spicy foods can also cause a runny nose due to a form of nonallergic rhinitis known as gustatory rhinitis. This isn’t caused by histamine or an allergen, but rather overstimulation of nerves in the sinuses when you eat or inhale something spicy.

The mucous membrane mistakes the spice for an irritant and goes into protective mode, triggering your nasal passage to produce extra mucus to remove the irritant. This is a temporary response, and a runny nose stops shortly after eating.

Eating foods with less spice can help stop this reaction.

Smoke is an irritant that can also trigger your mucous membrane to produce extra mucus. You may get a runny nose if you’re around smokers or in a smoke-filled room.

In most cases, removing yourself from a smoky area will reverse this reaction.

Hormonal changes during pregnancy can also lead to excess mucus and trigger a runny nose. It’s estimated that nonallergic rhinitis affects about 20 percent of pregnant women. In fact, it’s a common issue among women during pregnancy.

A runny nose can develop at any point during pregnancy, but symptoms usually disappear after delivery. Raising the head of your bed about 30 degrees and doing light to moderate exercise may help improve nasal symptoms.

Ask your doctor or pharmacist about antihistamines that are safe for use during pregnancy.

Common runny nose culprits include a cold and allergies, but it can also occur with other underlying issues.

A runny nose often clears on its own with self-care. However, see a doctor for nasal discharge that’s yellow or green, or accompanied by pain.

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